Microbiology Classification Systems

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Questions and Answers

What is the most common cause of UTIs?

E. coli (correct)

Mycobacterium

Serratia marcescens

Pseudomonas aeruginosa

What is the purpose of an acid-fast stain?

To detect lactose fermentation

To identify Mycobacterium tuberculosis (correct)

To detect Pseudomonas aeruginosa

To identify E. coli

What is the current classification scheme favored by most microbiologists?

Five-kingdom system

Two-kingdom system

Four-domain system

Three-domain system (correct)

What can be used to identify bacteria?

Colony morphology and metabolic capabilities Signup and view all the answers

What is the main difference between the five-kingdom system and the three-domain system?

The classification of prokaryotic organisms Signup and view all the answers

What is a characteristic of Pseudomonas aeruginosa?

Produces a soluble greenish pigment Signup and view all the answers

What is the name of the scientist who proposed the five-kingdom system?

R.H. Whittaker Signup and view all the answers

What is a characteristic of Serratia marcescens?

Produces a red pigment when incubated at 22°C Signup and view all the answers

What is a characteristic of E. coli?

Ferments lactose to form pink colonies Signup and view all the answers

Which domain includes single-celled eukaryotes?

Eukarya Signup and view all the answers

What is the name of the kingdom that includes plants in the five-kingdom system?

Plantae Signup and view all the answers

What is an example of a differential medium?

Both A and B Signup and view all the answers

What can be used to identify a microorganism?

All of the above Signup and view all the answers

Which of the following is an example of a prokaryotic organism?

Methano- bacterium Signup and view all the answers

What is the main characteristic that distinguishes Bacteria from Archaea?

Genetic differences Signup and view all the answers

Which of the following is NOT one of the five kingdoms in the five-kingdom system?

Archaea Signup and view all the answers

What is the main limitation of the five-kingdom system?

It does not recognize the distinction between Bacteria and Archaea Signup and view all the answers

What is the main advantage of the three-domain system?

It recognizes the distinction between Bacteria and Archaea Signup and view all the answers

What is the purpose of adding hydrogen peroxide in the catalase test?

To detect the presence of catalase enzyme Signup and view all the answers

What is the byproduct of urea degradation in the urease test?

Carbon dioxide and ammonia Signup and view all the answers

What is the function of an inverted tube in sugar fermentation test?

To trap any gas produced Signup and view all the answers

What is the minimum incubation period required for most biochemical tests?

18 hours Signup and view all the answers

What is the purpose of a dichotomous key in bacterial identification?

To lead to the identification of an organism Signup and view all the answers

What is detected in the Voges-Proskauer test?

Acetoin, an intermediate of the fermentation pathway Signup and view all the answers

What is the purpose of a pH indicator in the urease test?

To measure the acidity of the sample Signup and view all the answers

Why is catalase test considered one of the easiest and fastest biochemical tests?

Because it is a simple and rapid test Signup and view all the answers

What happens to the pH when an organism ferments sugar?

It lowers Signup and view all the answers

What is the purpose of a Gram stain?

To distinguish between Gram-positive and Gram-negative bacteria Signup and view all the answers

What does the 'O157' in E. coli O157:H7 refer to?

The serotype of E. coli Signup and view all the answers

Why are biochemical tests usually inoculated at the same time?

To save time and resources Signup and view all the answers

What is the purpose of gel electrophoresis in RFLP analysis?

To separate the fragments of DNA Signup and view all the answers

What is the significance of identical RFLPs in isolates of the same species?

They may or may not be the same strain Signup and view all the answers

What is the purpose of the oxidase test?

To identify Pseudomonas aeruginosa Signup and view all the answers

What is the result of a positive catalase test?

The decomposition of hydrogen peroxide Signup and view all the answers

What is the purpose of PulseNet established by the CDC?

To track foodborne disease outbreaks Signup and view all the answers

What is the purpose of the urease test?

To detect the presence of urease Signup and view all the answers

What is the advantage of multilocus sequence typing (MLST) over RFLP analysis?

MLST is more practical than RFLP analysis Signup and view all the answers

What is the purpose of restriction enzymes in RFLP analysis?

To cut the DNA into fragments Signup and view all the answers

What is the result of a negative coagulase test?

The absence of coagulase Signup and view all the answers

What is the purpose of a dichotomous key?

To identify the cause of urinary tract infections Signup and view all the answers

What is the unit of measurement used to express the size of restriction fragments?

Kilobase pairs Signup and view all the answers

What is the purpose of ethidium bromide in RFLP analysis?

To stain the fragments Signup and view all the answers

Study Notes

Classification Systems

The three-domain system is the most widely accepted classification system, dividing organisms into Bacteria, Archaea, and Eukarya.
The five-kingdom system, proposed by R.H. Whittaker in 1969, categorizes organisms into Plantae, Animalia, Fungi, Protista, and Prokaryotae.
The three-domain system recognizes the differences between prokaryotic and eukaryotic organisms.

Characteristics of Microorganisms

Colony morphology can give initial clues to the identity of an organism.
Metabolic capabilities, such as sugar fermentation and end products, are used to identify microorganisms.
Biochemical tests, like the Voges-Proskauer test, detect specific enzymes and metabolic pathways.

Biochemical Tests

The catalase test detects the presence of the enzyme catalase, which breaks down hydrogen peroxide.
The sugar fermentation test detects the production of acid and gas, resulting in a color change.
The urease test detects the presence of the enzyme urease, which breaks down urea to produce carbon dioxide and ammonia.

Identification of Microorganisms

A dichotomous key is used to identify bacteria based on biochemical tests and other characteristics.
The Gram stain is used to differentiate between Gram-positive and Gram-negative bacteria.
The oxidase test detects the presence of the enzyme oxidase.
The coagulase test detects the presence of the enzyme coagulase.

DNA-Based Identification

Restriction fragment length polymorphisms (RFLPs) are used to identify and track foodborne bacterial pathogens.
The CDC's PulseNet database catalogs RFLPs of certain foodborne bacterial pathogens.
Multilocus sequence typing (MLST) involves sequencing and comparing the DNA of different isolates to identify and track microorganisms.

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Description

Learn about the three-domain system and the five-kingdom system, and understand the characteristics of microorganisms. Explore the differences between prokaryotic and eukaryotic organisms.